Skip to main content

Full text of "An essay on the pathology of dental caries : written in competition for the Prize Medal, 1863"

See other formats

West Virginia University Libraries 

3 0802 102296257 4 


JUL 3 1968 






Digitized by the Internet Archive 

in 2012 with funding from 

LYRASIS Members and Sloan Foundation 











"Labor omnia vincit." — Peregrine. 






The part played by Electricity in the organic 
world lias long been a perplexing puzzle to the 
philosopher as well as to the physiologist. 

Its action in the animal system is looked upon 
as something distinct from that force which is 
usually denominated " vital," although it is ad- 
mitted there is much that may be considered as 
identical with it, — so much so, indeed, that it 
becomes a difficult question to decide whether 
the one or the other prevails, or to find a line of 
demarcation between them. In addition to this 
fact, there have been so many purely electrical 
phenomena at different times developed from the 
living subject as to have given rise to various 
hypothetical arrangements of batteries supposed 
to exist in the human frame ; and yet, strange to 
say, the one condition more than any other inti- 
mately associated with it has been the least 
attended to. Chemical action and electricity are 
known to be so far inseparable as to render it 
impossible that the one shall be produced without 
at the same time the other becoming manifest ; 
and it has been said by Professor Faraday, that 


" chemical action is often a more delicate test of 
electricity than the galvanometer ; yet, with the 
knowledge of electricity being thus developed in 
animal life, it is most surprising that hitherto, its 
electro-chemical effects in the living organism 
should have remained so little regarded. 

It has been demonstrated also by the same Pro- 
fessor, that " electricity, whatever may be its source, 
is identical in its nature;" and it was supposed 
by Dr. Wilson Philip " that the nerves which 
excite the muscles and effect the chemical changes 
of the vital functions, operate by the electric 
power supplied by the brain and spinal marrow, 
in its effects modified by the vital powers of the 
living animal ; because he found, that while the 
vital powers remain, all these functions can be 
as well performed by voltaic electricity after 
the removal of the nervous influence as by that 
influence itself." (Note by Faraday.*) 

It was announced by Professor Brande, that 
" when liquid albumen is made part of the voltaic 
circuit, it presents appearances dependent upon 
the power used, which, when considerable, excites 
so much heat as to coagulate it ; but with a feeble 
power and the poles sufficiently distant, coagula- 
tion ensues most plentifully at the negative plati- 
num wire ; a coagulum also forms at the positive 
wire, where acid is sparingly evolved." (Manual, 
p. 1138.) The preceding discovery having been 

* Phil. Transactions. 


made prior to the days of " electricity," its signi- 
ficance remained unheeded ; but the manner in 
which the metals are acted upon, in being repro- 
duced from their solution into the metallic state, 
and in any desired form, has become a fact so well 
known at this time, under the above title, or 
" Electro-Metallurgy," as to render it a matter of 
less surprise that organic material should be dealt 
with in a somewhat similar way. In experiment- 
ing with a viscous solution for a specific object, it 
was discovered that albumen from the egg, serum 
from the blood, milk, and other organic substances, 
were not merely " coagulated," but were disposed 
in a definite form and arrangement of parts, possess- 
ing characteristic peculiarities, in some instances 
resembling very closely some of those substances 
hitherto supposed to belong to that class usually 
regarded as " vital " productions. 

The earthy salts, likewise, are influenced in a 
peculiar manner. Not only are the salts of lime 
taken out of their original basis of bone or dentine 
and transferred to other localities and reproduced 
in the same or a different form of crystallization, 
but the acid may be separated from its base, leav- 
ing both the acid and the base either free and 
uncombined, or suffering both to form other com- 
binations. " Such," says Sir Humphry Davy, 
" are the decomposing powers of electricity that 
not even insoluble compounds are capable of re- 
sisting their energy; for even glass, sulphate of 


barytes, fluor spar, &c, when moistened and 
placed in contact with electrified surfaces from the 
voltaic apparatus, are slowly acted upon, and the 
alkaline, earthy, or acid matter carried to the poles 
in the common order." 

" The chemical action of voltaic electricity," says 
Faraday, " is characteristic of that agent, but not 
more characteristic than are the laws under which 
the bodies evolved by decomposition arrange them- 
selves at the poles." Thus, whenever acid ap- 
pears, it is invariably at the electro-positive pole, 
and may be taken as conclusive evidence of that 
condition, while the alkaline state evidences the 
e\ee\xo-negative. Hence the external layers of the 
skin, the mucous membrane of the mouth, &c, 
and the dentine of the tooth, are unquestionably 
in an electro-positive state, and consequently are 
liable to the development of acidity. The source 
of this acidity may be either the serum of the 
blood or the saliva — the latter of which is so 
easily decomposed that I have obtained enough 
electricity of sufficient intensity from a battery 
contained in a small silver thimble, with a few 
drops of diluted sulphuric acid, to redden litmus- 
paper in a few seconds when moistened with 

Now, although we have occasionally an acid 
condition developed in certain parts, and occurring 
at one time more than another, these, except 
perhaps in such cases as the gastric juice of the 


stomach, &c, may be considered as somewhat 
abnormal ; the normal action being that in which 
the change of elements goes on so slowly and 
regularly that the elements of each acid or basis 
may be appropriated as fast as they are liberated, 
and so taken up as not to be allowed sufficient 
time to manifest either acid or alkaline qualities. 

Under these circumstances it becomes extremely 
easy to explain all the phenomena of dental caries 
as being produced by electro-chemical action ; and 
as this abnormal action can be shown to be only 
part and parcel of its normal action as developed 
in other parts of the system, and can be demon- 
strated out of the system from the same materials 
by these same means, there are strong grounds 
for believing in their identity of action. 

There are cogent reasons also for assuming that 
if any great advance is to be made upon our 
present stock of physiological and pathological 
knowledge, it will have to be sought for in this 
direction ; and when there shall be found in one 
individual an Owen and a Faraday, or a Huxley 
and a Grove, combining the profound knowledge 
of the physiologist with the consummate skill and 
tact of the electrician, organic matter may stand 
a chance of being taken to pieces and tortured to 
confession, with as much pertinacity as that which 
has already compelled inorganic matter to yield 
up the history of its own existence. 


1. The pathology of a subject involved in so 
much obscurity as the one now under considera- 
tion, occurring as it does in a substance respecting 
which it has never yet been definitively settled 
whether it has to be regarded as a vital body 
possessed of vitality, or as merely a vital product 
amenable only to the ordinary physical laws of 
inanimate nature, can only be adequately treated 
by first determining to which of the two conditions 
it has the more legitimate claim. 

2. Until quite recently, the dentinal portion of 
the tooth has been regarded as part of the vitalized 
substance of the organ. Professor Bell observes : 
" That the teeth possess vitality; that they 
are connected by their organization with the 
general system, having nerves, blood-vessels, and 
absorbents, and are analogous in this respect to 
other bones, is a truth so strongly attested by all 
the phenomena they present, whether in a healthy 
or a diseased state, that it is difficult to imagine 
upon what grounds it can have been controverted, 
or even doubted, by any one whose opinions are 
deduced from observation or experiment. The 


question is not whether in the internal cavity of a 
tooth nerves and blood-vessels exist, for this is 
too obvious to require proof; but whether these 
essential components of animal organization do or 
do not enter into the composition of the tooth 

3. The existence of the dentinal tubes and the 
recent discovery of the dentinal occupants of the 
tubes (the soft fibrils of Tomes), and these being 
in connection with or extensions of the pulp into 
the substance of the dentine, might seem to give 
additional if not conclusive weight to the above 
argument ; but it has been shown by Messrs. 
Tomes and De Morgan* that dentine is not 
organized "like other bones;" there is no con- 
stantly recurring action of absorption and repro- 
duction going on in the dentine of the tooth, as 
has been demonstrated by these gentlemen to 
occur in ordinary bone. Besides this, we must 
take care no longer to suffer ourselves to be 
misled by mixing up the physical with the vital, 
so as to confound the purely vital condition of the 
pulp and its fibrils with the merely physical 
character of the dentine — a substance which forms 
only an exterior coating of a compound, though 
strictly physical nature, provided solely for a 
mechanical purpose, and bearing the same relation 
to the vital pulp of the tooth that the shell does to 
the egg or the rind to the orange. 

* Phil. Transactions. 


4. The only apparent action of vitality that 
can be traced in the tooth is in furnishing material 
for the subsequent depositing of new matter ; but 
this is strictly a physical result derived from an 
action of vitality in the pulp, which leads to its 
shielding itself with a further deposit of a non- 
vitalized protective covering. 

5. The pulp being endowed with feeling, is 
apparently capable of receiving impressions from 
abroad ; and this power of being irritated by 
external agents excites it to the exercise of its 
function in consolidating a zone of the tubes 
by means of its fibrils, so as to insulate itself 
from the irritant. This action clearly indicates 
the existence of some kind of condition ren- 
dering the proceeding desirable. To suppose it 
to arise from a " consciousness," is to ascribe to 
the pulp a degree of intelligence by no means in 
cordance with known and acknowledged facts. 
To assert that the want is telegraphed to the 
brain and a reply sent back from the depot at 
" head-qitarters," is a mere hypothetical as- 
sumption based upon no traceable knowledge 
of facts. 

6. But it is not needful to hypothesize, since it 
can be demonstrated by actual experiment that 
the production, electro-voltaically, of new matter 
under such circumstances is one of the inevitable 
consequences of the condition of the parts when 
and where it is formed, and that it is only the 


fulfilment of one of the laws pertaining to the 
electro-biology of the subject. 

7. All physiologists agree in admitting the 
probable existence of some kind of arrangement 
in the animal frame answering in its effects to an 
electrical battery, and we have most unquestionably 
a portion of such an arrangement constituting the 
outward coverings of the system. The peripheral 
layers, known as the skin, consist of three distinct 
parts — the outermost, or epidermis, composed of 
a series of scale-like laminge, constantly being 
formed from beneath, while the upper or external 
ones are simultaneously drying up and being 
cast off. 

8. The next layer immediately beneath the 
epidermis, the basement membrane, a thin homo- 
geneous, soft stratum of transparent and struc- 
tureless substance, identical with the material of 
the epidermis, but wanting the structural arrange- 
ment which, in its turn, converts it into the 

9. Below the basement membrane' lies the 
network of nerves and blood-vessels in a layer 
parallel with the outward surface of the cuticle. 

10. It is from these blood-vessels, contained 
in the cutis, or true skin, that the albuminous 
material is obtained, and is first formed into base- 
ment membrane, and then farther elaborated into 
the mucous layer of the cuticle. The liquor 
sanguinis, flowing through the capillaries in a 


regular and constant stream, furnishes a con- 
tinuous supply of fresh material, as portions 
become abstracted for local use ; and thus the 
whole of the soft structures outward of the blood- 
vessels are continually changing, through being 
formed and subsequently discarded. 

11. But it may be asked, In what way does all 
this constitute it a " galvanic battery ? " The 
answer is, that the condition and arrangement 
of the several layers are incontestably those of 
an electro-voltaic series, while the actions per- 
formed are essentially those of a voltaic com- 

12. If a plate of zinc, and a plate of copper or 
silver, be dipped into an electrolyte and made to 
touch each other, galvanic action ensues. The 
zinc, or positive pole, develops acidity and is 
wasted in bulk, while the liquid, or electrolyte, 
is decomposed, and its elements are carried 
different ways, one part to the zinc and the other 
to the copper ; or, as is shown in the Appendix, 
when albuminous matter is acted upon, although 
the water and various salts it may contain will be 
decomposed, the albumen itself is arranged in a 
definite form. 

13. It has been asserted by Professor Faraday, 
that such elements as are most powerfully com- 
bined are the easiest to be decomposed ; but that 
substances held together with a very feeble 
affinity, such as albuminous matter, of which all 


organized beings principally consist, are extremely 
difficult of decomposition. In this we see a 
beautiful provision of Nature, and also a fact 
which tells most forcibly in favour of the belief 
that the electrical force developed and maintained 
by the vital arrangement is the agent employed 
by the all-wise Creator in moulding organic 
matter into the various forms and bodies required 
in carrying out the materialization of the living 

14. It has been demonstrated* that albuminous 
matter is not merely consolidated by the electro- 
voltaic force, but that it also assumes a kind of 
organization. The material at each pole pos- 
sesses a special and distinct character, at the 
same time that a solid wall of structural substance 
grows up between them at the point where the 
two conditions of the force may be supposed to 
meet, spreading out quite across the vessel, and 
forming a membranous diaphragm or partition, 
dividing into two compartments the two portions 
of the electrolyte in opposite states, correspond- 
ing to the condition of the pole immersed in it. 
In electro-metallurgy the precipitated metal ad- 
heres to the negative pole, but with albumen it 
recedes from the pole, thus in nature preventing 
the negative vessels becoming clogged by a 
casing of their own depositing. 

15. This, however, is not all; the salts of lime 

* See Appendix. B. 


contained in the albumen, or added to it, become 
arranged organically within the substance of this 
diaphragm, constituting it a membranous matrix, 
which corresponds with and occupies the place of 
the under part of the basement membrane in the 
skin, and the dentine in the tooth. We have thus 
a double result, — first, the production from the 
liquid albumen of a solid membranous matrix, 
and its then becoming tenanted by the salts of 
lime, converting that which was at first only a 
piece of tough and elastic "gristle" into a hard 
and stony mass. 

16. In addition to this, we find the consolidated 
material arising on the positive side of the trans- 
verse ' matrix containing unmistakeable proofs 
of acidity, while the negative side is neutral or 

17. Reverting now to the conditions and 
arrangement of the parts comprising the skin, 
or " Peripheral Battery " of the animal system, it 
may be stated, that when giving out albuminous 
material for new growth, the blood is invariably 
in an alkaline state ; and therefore, if the part 
be in an electrical condition at all — and Sir Hum- 
phry Davy came to the conclusion that all bodies 
in nature were in one or the other of the two 
electric states — it cannot be positive, and must 
consequently be negative. For the same reason 
that the alkaline blood-vessels must be negative, 
the epidermis, or the epithelium, must be positive; 



and on being tested with blue litmus-paper, it will 
be found to be less commonly neutral than giving 
strong proofs of acidity. "We have, lastly, the 
albuminous matter from the blood-vessels, in the 
formation of the basement membrane, spreading 
out laterally between the two electrodes, the 
cutis and the cuticle, in the form of basement 
membrane, precisely in the same manner as has 
been observed to take place artificially. 

18. In tracing the correspondence still further, 
we shall find the several membranes of the skin 
answering in their actions to the electro-polar 
condition of an electrolyte, or matter in a state 
of induction between the two electrodes.* 

19. If a piece of metal be suspended in a so- 
lution capable of dissolving it, and through which 
an electric current be made to pass, one portion 
will be dissolved, while the portion on the opposite 
side will be added to by a new deposit; and 
should there be three or four, or more, each one 
will be affected in a similar manner, the wasting 
end or side of one being always opposed to the 
increasing or growing side of the next in suc- 

* It has been deemed unnecessary to make any allusion to the great 
central part of the battery in connection with the brain and other 
internal organs, as the arrangement and construction of any small por- 
tion of it explains the condition of the whole, which is but a repetition 
on a different scale. It is the action and the electro-chemical effects 
that are more particularly required to be brought under notice, for the 
same description of changes which are produced in one part of the 
battery takes place in all. 


20. In depositing metals, the new deposit forms 
upon or in contact with the negative plate ; but 
with albumen, as previously stated, the solidified 
portion recedes from it ; so that if the wire from 
the battery were a hollow tube, furnishing a 
continuous supply, it would lead to the gradual 
increase of the solid part forming around it, and 
to its being driven outwards and away from the 
centre by new layers added to its interior. Thus 
the inner side becomes the negative or growing 
side, while the outer, presenting itself to the 
positive pole, is the absorbing or acid surface. 

21. Referring now to the analogous condition of 
the skin, the vessels of the cutis may be taken to 
represent the hollow negative pole giving out its 
continuous supply of albumen, and the basement 
membrane that of the consolidated substance 
immediately resulting from it. This, from its 
position, will have its inner side negative and 
grouting, and consequently its upper side positive 
and. wasting. The cuticle above it will also be 
in a corresponding condition of increase below 
and waste above. It is only in accordance with 
the preceding facts (19) that the wasting upper 
surface of the basement membrane should pass 
to the under or increasing surface of the cuticle ; 
and although, microscopically considered, no two 
substances can be less alike, yet the chemist is able 
to recognize the material of the two as identical 
in composition, while the electrotypist has become 

b 2 


perfectly familiar with transformations equally 
remarkable, occurring under the moulding in- 
fluence of electricity. 

22. We observe in the tooth papilla, when in- 
closed in its follicle and commencing to change 
itself into the tooth, that the new matter no 
longer goes to form basement membrane, but pro- 
ceeds to accumulate beneath It, forming the mem- 
branous matrix of the dentine, which, so formed, 
then occupies the place formerly filled by the 
increasing portion of the basement membrane. 

23. The state of the epidermis and of the epi- 
thelium being electro-positive and forming part of 
the peripheral battery, when these substances 
disappear and are replaced by another form of 
covering, as epithelium instead of epidermis, or 
dentine instead of epithelium, each of these must 
necessarily be in a similar condition. The fact, 
however, readily admits of demonstration, as will 
presently be seen by experiment. 

24. Dental caries has been defined as "the 
death and subsequent progressive decomposition 
of the dentine." But to accept this definition, we 
shall have to acknowledge a "life" or "vitality" 
to have previously existed ; for there can be no 
death in that which never possessed life.* It has 
been demonstrated that dentine can have no claim 
to vitality in the usual acceptation of the term : 
not having in itself the power of growth or of 

*. Appendix A. 


performing any other function of vitality, it can 
therefore be only regarded in the light of a "vital 
product," having an organized form and liable to 
the same physical changes to which other forms of 
organic matter have to succumb. 

25. The discoloration of the dentine, which has 
been supposed to have arisen from its " death," 
is shown by the chemist to be only an ordinary 
form of decay, occurring under certain conditions 
in an organic substance : it is termed eremacausis, 
or slow combustion, the peculiar feature being a 
slow conversion of some of the elements, while the 
carbon remains as charcoal. The conditions under 
which it occurs, depending entirely upon adven- 
titious circumstances, are purely physical. 

26. With regard to the progressive decom- 
position of decay, it has been proved experimen- 
tally that under the positive pole of an electro- 
voltaic battery the lime is taken out of dentine, 
and the decalcified structure is invariably more 
or less acid — in both these respects correspond- 
ing with the main features present in dental 
caries, and as the electrical condition which could 
give rise to these effects will be shown to exist, 
the sequence must be accepted as an inevitable 
and natural result of such a condition. The 
production of acidity in carious dentine has been 
attributed to decaying food : no bulk of food 
would be able to produce, under any circum- 
stances, one half the amount of acid often found 


in a small cavity ; and were the production of 
the acid external, decaying teeth would never 
be coated with tartar, as will commonly be found 
to occur (Fig. 1, Plate 1). A strongly acid carious 
cavity and tartar upon and around the necks of 
the teeth, together with an acid state of the gums, 
is a circumstance of frequent occurrence. A com- 
plete illustration of this may be seen in a specimen 
contained in the museum of the Odontological 
Society, where, in a tooth largely coated with 
tartar, the acid fluid running out of the carious 
cavity has furrowed away the tartar by dissolving 
it, immediately beloiv the cavity, and showing its 
source to be within it. 

27. In a normally balanced electro-vital action 
the elements appear to separate and re-combine so 
as to produce results in a neutral state, but which 
in an abnormal and unbalanced action give rise to 
the production of free acid, &c. ; thus, in the 
mouth, the gums may be perfectly neutral at times, 
but powerfully acid at others, and yet the teeth are 
not acted upon by the acid unless some physical 
defect exists in their structure or upon their 
surface. If we look closely into the starting- 
point of decay, we shall find that a change takes 
place first in the organic matrix either of the 
dentine or its enamel, and before the acid stage 
can be detected, and that often the same corroding 
action that is seen in the dentine may be shown 
to have taken place in the enamel previous to its 


reaching the dentine, as at a (Fig. 2, Plate 1) ; 
thus showing that both substances are affected 
in the same way, although in a different degree, 
owing to the different amount of organic matter 
of which they respectively consist. If we take 
the specimen Fig. 3, Plate 1, it will be seen 
that a corroding effect has begun at the fissure 
in the enamel, while a stained spot with a 
deeply darkened upper surface extends into the 

28. Referring now to specimen Fig. 4, Plate 1, 
we have a similar formation existing in a tooth, but 
in an earlier stage of decay, or rather before any 
signs of coming decay have made their appearance : 
taken singly, it tells nothing; but on being sub- 
jected to electro- decalcification, new facts have 
become revealed. The positive or decalcifying 
pole was made to rest at p, while the negative 
pole was placed at n. After a few hours' action, 
it was found that a portion of albumen had become 
consolidated upon the fissure a, spreading to the 
round spot below it, thus screening them from 
the decalcifying action of the battery, and showing 
them to be electro-negative, the same as the part n. 
Here, then, we have evidence of " local action " 
and a starting-point for the commencement of the 
acidifying stage of decay. 

* This staining of the subjacent dentine would seem to be due rather 
to the having imbibed colouring matter from the decayed portion, than 
from any change itself has undergone. 


29. It is well known that some forms of carbon 
or charcoal are amongst the most powerfully elec- 
tro-negative bodies in nature, and when the tooth 
(Fig. 4, Plate 1) was first ground down and placed 
in the albumen, the fissure teas filled with a 
black carbonaceous mass, which subsequently came 
away in the cleaning. This, then, was a negative 
point (charcoal) in a positive substance (dentine), 
and had it been left to its fate in the mouth, the 
negative point of charcoal, becoming imbued with 
saliva, would in time have become the developer 
of acid, and carried the process on to the stage 
represented in specimen Fig. 3, Plate 1 ; further 
stih in Fig. 2, Plate 1. 

30. Respecting local electro-voltaic action, Pro- 
fessor Grove says, " If a plate of pure zinc be 
immersed in dilute sulphuric acid, little or no 
chemical action takes place ; but keep in contact 
with the zinc another metal, say an iron nail, and 
the zinc is rapidly oxidated and dissolved, hydrogen 
being evolved from the surface of the iron. The 
action is most rapid at the points most proximate 
to the iron ; so that, if the nail be laid upon the 
zinc, both being immersed in the liquid, the iron 
would seem to eat its way into the zinc. If a few 
iron filings be placed upon the zinc, the action will 
be similar, but will begin more slowly and increase 
as the points of iron are exposed, these latter 
being protected to a great extent by their being 
negative and coated with hydrogen. If an infini- 


tesimal quantity of copper be dissolved in the 
acid, it will be precipitated in a metallic state on 
the negative points, and make these permanent 
centres of action. So, if no iron be made to touch 
the zinc, after a time some want of absolute homo- 
geneity is sure to determine a chemical action; 
and as any trace of metal existing in the solution 
will by this chemical (or rather electrolytic) action 
be deposited on the negative point, or those least 
attached, the action will continually increase, and, 
instead of being uniform, will be in patches around 
the negative centres. Thus a piece of common 
zinc of commerce, which contains small portions 
of iron and tin, will be corroded in pits and holes. 
With imperfectly conducting bodies the action 
is similar ; at very short distances they conduct, 
and the action spreads or extends from a point to 
the surrounding points. The effects all proceed 
from a want of perfect homogeneity, either original 
or impressed by some very trifling circumstance, 
and from the fact, that points of action having 
once been established, the corrosion is increased 
by the effects it itself produces and the deposits it 
forms. A dentist, to cure a carious tooth, scrapes 
out all the diseased parts, &c." The above letter 
to the author of the " British Mollusca,"* in ex- 
planation of "substances apparently homogeneous" 
being " corroded in patches or irregular hollows," 
with reference more especially to the shells of 

* British Conchology, by J. Gwyn Jeffreys, F.R.S. 


molluscs, affords a most perfect illustration of our 
present subject. 

31. To obtain a practical illustration of the 
effects resulting from a negative point of carbon, a 
perfectly sound bicuspid was ground down so as 
to provide a thick section : in the enamel of this, 
two cuts, one on each side, were made with a fine 
dividing-file, and one of them filled with carbon 
made into a paste with saliva, the other remaining 
as left by the file. The section (Fig. 5, Plate 1) 
thus prepared was placed in saliva, the positive 
pole resting at p, the negative at n, and subjected 
to about twenty hours' decalcification. 

32. It will be seen that the dentine around p, 
which has been acted upon, and which was origin- 
ally colourless, as also was the saliva, has become 
tinged of a yellowish brown up to the shaded part 
a ; and also, that while the notch on the right- 
hand side has been rendered wider and shallower, 
the notch containing the carbon, as well as the 
out eredge of the enamel itself, remains as sharp 
as when first cut. The decalcifying action of the 
positive pole has thus included the enamel at the 
top and right-hand side of the section ; but the 
left-hand portion, represented by the shaded part 
in the accompanying figure, has been rendered 
negative by the carbon, and hence become coated 
with a deposit instead. A more decisive proof of 
the electro-negative effect of carbon, as a source 
of local action, cannot be desired ; and, had time 


permitted, there is not a question but that by a 
delicately adjusted balance of feeble electrical 
action continued over a longer space of time, all 
the phenomena of its producing local acidity might 
have been obtained, as has since been done with 
a metallic plug of tin (paragraph 34). As it is, 
however, its action is unmistakeable ; and if a 
piece of damp litmus-paper be pressed upon the 
surface, all the decalcified portion will be found to 
be strongly acid, while the shaded or negative 
portion is still neutral or alkaline.* 

33. This local action engendered, it can only 
be stayed by removing or rendering inactive the 
negative part or excluding the electrolyte so as to 
destroy the means of farther electro-voltaic de- 
composition ; and it will not fail to be recognized 
that this is the exact process we invariably resort 
to in the treatment of dental caries. We know by 
experience that not only must all the injured part 
be removed, but we must endeavour to exclude the 

* The particular acids traceable in the mouth depend very greatly 
upon what elements the electrolyte may have held in solution at the 
time, and to show that substances taken internally are detectable in the 
fluids of the mouth. A piece of white paper, moistened with saliva 
from a source where three grains of iodide of potassium were being 
taken thrice a day, five hours after the last dose, was touched with the 
platinum wires of the battery, when the iodine was instantaneously 
manifested by the violet stain of the starch test supplied in the sizing 
of the paper. The deep yellow stain often seen at the necks of the 
teeth and in the decay of the fangs, may in the same way be com- 
municated by minute portions of iodine in the system, as has been 
done with Fig. 6, Plate 1, which was acted upon in saliva from the same 
source as the preceding. 


moisture, to prevent its relapsing into the same 

34. These electrical conditions may also serve 
to throw some light on a circumstance respecting 
which very little is at present known — that is, 
why some substances answer better for filling the 
cavity in a decayed tooth than others. Respect- 
ing this question a most interesting and highly 
important fact has just been brought to light, 
which may assist very materially in determining 
the suitability of a metallic substance for the pur- 
pose. The idea suggested itself as to what might 
be the relative electrical condition of the several 
metallic stoppings now in use with regard to the 
electrical condition of the dentine, and it was 
found on experiment that while gold was positive 
and in the same condition as the dentine, tin was 
powerfully negative, and in this respect in the 
same relative state as the carbon, and conse- 
quently an unsuitable metal for a stopping. Nor 
is this all, for it was also found that with the tin 
plug a strongly marked acidifying local action was 
produced. A plug of tinfoil was made in a piece 
of dentine and placed under the influence of a 
current of electricity ; a piece of litmus-paper was 
then moistened with salt and water, and placed upon 
the surface, with the positive pole resting at p and 
the negative pole at n (Fig. 7, Plate 1). The effect 
after a few minutes is represented in Fig. 2, Plate 2; 
it being impossible to preserve or dry the litmus- 


paper without the acid. A metallic plug of gold 
being in the same electrical condition as the 
crown of the tooth, is a perfectly inactive agent, 
beyond the mere effect of pressure and confine- 
ment of any fluid that may exude from the pulp ; 
whereas, any other metal that may be negative to 
the crown of the tooth induces local action, whereof 
the acidifying pole is opposed to the negative 
pole of the tooth, which is its fang; and hence this 
condition accounts for the decay so constantly 
occurring in lateral stoppings at or below the free 
edge of the gums (Fig. 1, Plate 2). A plug 
of gold was substituted for the tin, and the 
spot, instead of being blue, was merely reddened, 
without the slightest trace of local or induced 
action. In the tin we have a strongly- marked 
reaction developed in the spot nearest to the 
negative pole, which corresponds with a metallic 
stopping in the side of a tooth tending to become 
imperfect, most at the point nearest to the fang 
or negative part of the tooth, because it is here 
the polarity of the plug produces the polar con- 
dition which first leads to the generation of the 
acid. Other metals have been tried with the most 
decided results (Figs. 3, 4, 5 and 6, Plate 2) ; 
but the comparison of them is irrelevant to 
the present subject, besides requiring still fur- 
ther investigation : the fact alone has only been 
brought forward as another instance of the cor- 
roboration afforded by the phenomena of electricity 


for establishing the identity of the results occur- 
ring both in and out of the mouth as proceeding 
from the same physical source. 

35. In pursuing the experiments in electro- 
decalcification, it was found that while it could be 
effected in water alone, there were other media by 
which it could be more rapidly and more exten- 
sively produced. Thus a weak solution of sugar 
and water was found to be more active than water 
alone, but albumen from the egg and serum from 
the blood proved far more powerful agents, partly 
through forming better conductors by their vis- 
cidity, and also apparently from the decomposition 
of the chloride of sodium they contain, forming 
hydrochloric acid and chlorine ; the saliva, too, is 
more active when thickened with mucus than 
in a less viscid state. Specimen Fig. 8, Plate 1, 
is an upper molar sawn through the centre of 
a decayed cavity. The part b is seen as left by 
the saw : the other part, a, shows its condition 
after twenty hours' decalcification in a weak solu- 
tion of sugar and water. The pulp-cavity in the 
part b is perfectly free from decay within, and 
contains large masses of secondary dentine, while 
the part a has had the decay extended arti- 
ficially, and in the absence of the negative pulp- 
vessels the cavity has also become enlarged. 
Specimen Fig. 9, Plate 1, has been treated in 
albumen thickened with a portion of the yolk, 
showing that the more viscid the medium within 


certain limits, the more diffused will be tlie decal- 
cifying effects. 

36. In all cases the decalcified dentine will be 
found to be strongly acid, and whenever a fluid 
containing albumen has been employed, there is 
invariably found an adhering portion of consoli- 
dated substance between the two poles, as at a 
(Fig. 9, Plate 1) ; and hence we have an effect 
exactly similar to the production of the trans- 
parent zones which form around a decaying 
centre, and therefore have no need to seek for the 
cause of the latter in a vital action, when it is 
shown to be a natural consequence of the physical 
condition of the parts concerned. 

37. The amount of substance produced in this 
part, however, is but small in comparison with 
what takes place in the pulp-cavity under more 
extensive excitement, the pulp itself being some- 
times almost obliterated ; but as these calcareous 
deposits can be so perfectly imitated by artificial 
means, there can be no doubt of their non-vital 
but physical source. 

38. It will have been observed, that the pulp- 
cavity once reached is rarely opened out much 
by decay, but the carious cavity tends to en- 
largement laterally (b Fig. 8, a Fig. 10, a Fig. 11, 
Plate 1). Were the pulp in a positive state, 
like the dentine, and like the pole of the battery 
which rested at p (Fig. 8, Plate 1), its moisture 
and action would have tended to enlarge the pulp- 


cavity so as to throw this and the carious cavity 
into one; but its being electro-negative, the pulp- 
cavity is protected from being electro-voltaically 
acted upon ; and we see this same condition 
further extended in the state of the dentinal 
fibrils, as continuations of the pulp. Mr. Tomes 
has informed us that the connecting material is 
usually the first, and the walls of the tubes the 
last, to become disintegrated. So that while the 
negative pulp protects the cavity, the negative 
fibrils protect the walls of the tubes ; and thus 
we have a consistent explanation of the whole 
proceeding. But when this action is going on, 
the tendency to new formation through the 
electro-voltaic action, leads to the consolidation 
of the fibrils in the early stage, and later, to an 
accumulation within the pulp, while the cavity 
itself mostly becomes added to on its inner 
surface, so as to lessen its dimensions — a tendency 
advantageously exerted when it leads to " cal- 
cification" of the exposed surface of the pulp. 
But the latter action is commonly attributed to 
the vital powers in the tooth. Unquestionably, if 
there were no vital powers in the tooth, it could 
not take place ; but the vital part of the action 
is confined to the circulation of the albuminous 
material in the arteries, veins, and capillaries of 
the pulp. The connection of the latter with those 
of the cutis shows the pulp to belong to the 
cutis, which is the negative layer of the peripheral 


battery, and to be hence endowed with the same 
acting powers ; but all the appearance of vitality 
possessed by the layers outward of the pulp is 
due to their being electro-voltaically arranged and 
acted upon. The tooth papilla growing from its 
infancy to its full size and shape in the dental 
follicle, is purely an act of vitality by cell-growth, 
with a design and a purpose. But the embryo 
tooth thus produced is a soft material, requiring 
farther elaboration ; therefore a secondary action 
of a purely physical character is then induced, 
which leads to its becoming encased with enamel 
and dentine. The vitality of the pulp furnishes 
the material for these changes, but the electro- 
voltaic arrangement of the tissues converts them, 
by a kind of galvano-plastic process, into an 
organic form. 

39. The circulation of the albuminous fluid out 
of which they are formed is due to the vitality 
of the vessels, and their connection with the 
general vitalization of the organism ; but its being 
exuded when new substance is about to be formed, 
is owing to the electrical condition of the parts, 
by which it is not only abstracted when it is 
wanted, but is also disposed of under certain 
fixed and definite laws, in the special form re- 

40. Having thus traced out the electrical or- 
ganization of the peripheral battery of the system, 
which includes the dentine as a part of it, and 


having also shown the " progressive decomposi- 
tion" of the enamel and dentine to be due to 
local electro-voltaic action, it remains to be seen 
under what circumstances the earlier stages of 
decay have their origin, and how far they may 
be likely to be affected by the secretions of the 
mouth or other adventitious circumstances. 

41. It is one of the laws of nature, that, in 
organic matter in a moist state, stagnation leads 
to a change. In all living forms a special organi- 
zation is provided for the fluids which are re- 
quired in growth to be kept in constant motion. 
When this organized structure is either bruised, 
broken down, or otherwise injured, so as to 
prevent the capillary action by which the moisture 
is passed on, the injured part is thus shut off 
from the circulation, and, according as it may 
contain little or much moisture, in time becomes 
decomposed or rotten. 

42. In the organization of the tooth, the soft 
fibrils extend to the enamel, and sometimes into 
it ; and as we know the enamel to be capable of 
absorbing moisture after being suffered to dry, we 
have a right to infer that it, as well as the other 
coverings of the cutis, is capable of giving off 
moisture in the same way as may be traced in 
the insensible perspiration of the skin ; and, in 
fact, we have no reason to doubt this when 
moisture may be collected readily from over 
the finger-nails, and therefore may take this as a 


clue to some of the more obscure conditions pre- 
disposing to the commencement of decay. 

43. In mouths imbued with thick and glairy- 
secretions of mucus, it is well known that the 
gums are generally less healthy, and the teeth 
more prone to decay and more rapid in their 
decaying, than where the saliva is less viscid. 
That this should be the case would be inferred 
from the analogous effects upon the human system 
generally under corresponding conditions : when 
placed in an atmosphere so saturated with mois- 
ture that the insensible perspiration is unable to 
escape, sickness and disease are certain to result. 
In Fig. 12, Plate 1, we have a good illustration 
of the effects of stagnant moisture upon a de- 
nuded surface of dentine. On the lower face 
of the notch, which, from its having been on a 
level with and parallel to the line of the gums, 
would have been kept constantly immersed in 
the saliva, eremacausis and decay have taken 
place ; while on the upper face, the surface in- 
clined downwards and equally free from friction, 
still retains its polish, and is perfectly free from 

* The immediate cause of the production of these notches, as well as 
the denuded portions of the facial surfaces and edges of the incisor 
teeth, has never yet been satisfactorily explained. In Pigs. 13 and 14, 
a portion of a sound and healthy tooth has been electro-voltaically 
acted upon partially, so as to leave an indentation with the peculiar 
sharp edge which is a characteristic feature in these occurrences. It 
has also left a degree of polish very different to what is produced by 
the reaction of an acid in the ordinary way, thus showing a strong 

c 2 


44. The condition of dentine placed in the 
mouth, artificially, corresponds fully with the pre- 
ceding case : where friction keeps the part free 
from stagnant moisture, its homogeneity is pre- 
served ; but where moisture is allowed to become 
stagnant, a change soon occurs ; the part thus 
soddened with moisture becomes a prey to the 
local action of the saliva, which has been shown 
to be a powerful electrolytic destroyer of dentine.* 
It is well known that where an artificial denture 
of ivory is acted upon by friction in the mouth, 
its polish is preserved, although other parts be- 
come decayed ; but these polished portions after a 
time mftstly become dark and discoloured ; the 
retention of the polish is most confirmatory evi- 
dence of the entire absence of all acid reaction 
ujDon the part from any acidity of the saliva, and 
proves the change most indisputably to be a prior 
occurrence to the production of the acid, and 
" from the fact that, points of action having once 
been established, the corrosion is increased by the 
effects itself produces " (sect. 30). The negative 
points thus established so.on set up sufficient local 

ground for attributing the natural occurrence to this same electro- 
voltaic action, as effected by the positive surface of epithelium of the 
lips in contact with them, it being the conduct of a positive pole to 
transfer the alkaline matter to the negative layer. 

* b, Fig. 11, Plate I., is one part of a divided molar, showing forty- 
eight hours' decalcification in saliva. The positive pole was made to 
rest on the edge of the original decay, so as to produce its extension ; 
and to what extent this has been effected will be seen by comparing 
the two portions, a and b. 


action to decompose both the dentine and the 
saliva, leaving the softened tissue — the decalcified 
membranous matrix of the dentine — to extend its 
action by its own effects. That it is capable of 
doing this, and that the negative condition of the 
element first giving rise to decay is continued in 
the same state as the decay proceeds, is proved by 
the following experiment. A molar tooth, which 
had lost about one half its crown by decay, was 
sawn through the middle, as near as possible, into 
two equal parts. One of these (a, Fig. 10, Plate 1) 
remains as cut ; the other (b, Fig. 10, Plate 1) has 
been twenty-four hours under action in saliva. The 
positive pole was placed at p, the negative at n. 
Had the crown of the tooth been in a homogeneous 
state, the decalcification would have extended 
across the upper or positive half of the tooth, as it 
has done in Figs. 9 and 15, Plate 1 ; but instead of 
this, the surface of the cavity has become lined with 
concretions of lime removed from the decalcified den- 
tine by the side of it. This is a conclusive proof that 
the surface upon which the lime rests is electro- 
negative. Were it otherwise, it could not have 
been so deposited ; its electro-negative condition 
has preserved it, in the same manner as did 
the tartar in Fig. 5, Plate 1. We have also in 
the specimen b (Fig. 10, Plate 1) a very intel- 
ligible explanation of the accumulation of tartar 
upon the necks of the teeth. The crown of the 
tooth being analogous to the outer layers of the 


skin, is consequently electropositive, a fact which 
is proved by the occurrence of acid within its 
substance ; but the fang of the tooth, from its con- 
nection with the cutis, through the vessels of the 
periosteum, is electro-negative; and hence, when 
any decomposition may be going on which produces 
a supply of the alkaline matter, it is attracted to 
the exposed portion of the negative under the free 
edge of the gum as a natural consequence of its 
condition.* In Fig. 11, Plate 1, the positive pole 
was placed on the edge of the pulp-cavity ; con- 
sequently the power of the battery overcame 
the more feeble power of the carbon and set up 
positive action in the two cavities, the pulp-cavity 
and the carious cavity ; but in Fig. 10, Plate 1, the 
pole resting in the centre of the sound dentine 
was sufficiently distant to be unable to overcome 
the negative tendency of the carious cavity ; and 
hence the latter became the recipient of the lime, 
as the most intensified negative part of the action. f 

* The author has always felt assured of the accumulation of tartar 
upon the necks of the teeth being due to something more than simple 
deposit of an ordinary precipitate from the saliva ; because the mere 
lodgement alone would not in preference take place around the necks 
of the teeth and upon upright surfaces, and attain its great degree of 
hardness, without some attractive force compelling its cohering and its 

f In the same manner that the fang of the tooth sometimes has its 
electrical state reversed from the negative to the positive, so the enamel, 
when active decay is taking place, often becomes negative and receives 
a coating of tartar up to the very edge of the cavity ; a state which 
protects the enamel from being acted upon, and causes it to become 
undermined, as in the specimen Fig. 1, Plate 1. 


Thus it is by the surface of a carious spot retaining 
its electro-negative state and increasing its area, 
that it becomes the extender of the mischief 
itself produces. 

45. It will have been seen that electro-chemical 
decomposition depends very greatly for its amount 
and rapidity of action upon the condition of the 
electrolyte or fluid element of the series ; and as the 
state of the fluids in the system is known to vary 
very much in health as well as in disease, and to 
be considerably affected by various medicaments 
taken internally, this difference at different 
times is abundantly sufficient to account for the 
tendency to decay at one time more than another 
without any very apparent cause. 

46. It has been shown that the arrangement of 
the several layers of the skin, and the several 
layers of the tooth — the enamel and dentine (as 
one) and the pulp are in opposite electrical states, 
and correspond in disposition and effects with a 
galvanic series, and that the formation of dentine 
as a physical result derived from its action is 
amply borne out by experiment ; hence there can 
be little question as to other consequences arising 
from the same arrangement, " for no voltaic bat- 
tery has as yet been constructed in which the 
chemical action is only that of combination;" 
" decomposition is always included, and is, I be- 
lieve," says Professor Faraday, " an essential 
chemical part" (858); and thus we may very 


justly attribute the decomposing effects in decay- 
to the same cause. 

47. In endeavouring to illustrate this subject 
with a series of results which as near as possible 
should correspond with the natural occurrences in 
the mouth, a number of new and highly interesting 
facts have been pointed out ; and, as Sir Humphry 
Davy remarks, " Concerning the publication of 
novel facts there can be but one judgment, for 
facts are independent of fashion, taste, and caprice, 
and are subject to no code of criticism ; they are 
more useful, perhaps, even when they contradict 
than when they support received doctrines, for our 
theories are only imperfect approximations to the 
real knowledge of things ; and in physical research, 
doubt is usually of excellent effect, for it is a 
principal motive for new labours, and leads con- 
tinually to the development of truth." 





- *m 



f r 

*™^. , ,,v 


| ,/r/. et /-'/■ 


fit 3 

Blue litmus Paper moistened 
with boiled water and subjected 
to Electro voltaic decomposition'. 

F12 4 

Ditto with water in which 

decayed teeth have been 


Fig 5 

Ditto with saliva 
li> mutatis 

Fig 7. 


Electro-bone substance nitli time 

globules shewing positive side ouzdn 

negatm side alkaline 

Fig 6 

Ditt,' with salt 
5$? to the 01 

J mui ales 

4,5 & 6 shewing the bleaching effects of chlorine evolved from the dilorule of' sodium 

W VA.-st, Jiromu.lith, 




In what does vitality consist ? If we take an egg, a 
nut, or a seed, and place it under the particular circum- 
stances required for enabling its powers of vitality to 
become manifest, we obtain by such means a special 
result, in the growth and development of a living 
organism. But if we break up the egg, split open 
the nut, or crush the seed, although every atom of their 
respective contents may be present, their power of 
growth will have ceased to exist. They will have lost 
their vitality. 

If we take a pip from an orange, a lemon, or an apple, 
each one contains within itself that which enables it to 
grow. It is the seat of life. It possesses " vitality." 
But if we take cells from the pulp, or a slice from the 
rind, although each one is equally a product of vitality, 
we shall obtain no development of a plant by then* 
growth, simply because they were never intended to 
grow, and hence were never endowed with " vitality." 

We may take a cutting, a bud, or in some cases a 
leaf, or even part of a leaf, from a plant, and each one 
can be made to develop itself into a living and growing 
individual, identical with its parent form ; but split off 
the bark from the cutting, break asunder the bud, or 
tear open the leaf, and the power to grow ceases with 
the separation of the parts. All that has been destroyed 
has been the arrangement of the substance which consti- 
tuted its condition of vitality. 

If we take for a cutting a portion of the stem of a 


rose, it is indispensable that it should contain a bud or 
" eye/' because the bud or eve alone possesses the con- 
dition of vitality essential to its growth, the stem being 
only an accessory and unessential part of the arrange- 
ment for growing ; it therefore is not endowed with 
vitality. The same may be said of the skin. In all 
rhino-plastic operations, it is necessary to include with 
the transplanted flap a portion of the cutis, because the 
vessels of this part alone contain the essentials of 
growth. There is, however, one other condition ne- 
cessary to success; which is, that the vessels of the 
transplanted portion must remain, or be placed in 
connection with the circulating fluids of the system. 
Their vitality is not inherent in the vessels themselves, 
but depends upon their forming a portion of the general 
vitalization of the organs ; and hence the circulation of 
the blood within them i3 one of the conditions consti- 
tuting their vitality. What we are to understand by 
"vitality," then, is the being possessed of that special 
arrangement of parts, which, out of unorganized matter 
elaborated in the system, leads to the development of 
organized forms and the powers and functions of Uft . 

In this respect the cuticle and basement membrane, 
independently of the vessels of the cutis, have no power 
of organizing fresh material; while stripped of their 
coverings, the cutis, or true skin, is enabled to repair 
the deficiency by organizing for itself a new formation 
in the place of the part removed. Here, then, we have 
the cuticle evidently subordinate to and resulting from 
the vitalized arrangement of the capillaries of the cutis ; 
and as the vitalized organization of the system has need 
of non-vitalized adjuncts to enable it to carry out the 
special duty of the different functions of the vital 
organism, it thus provides the bones, muscles, tendons, 
ligaments, membranes, &c, which serve for its aid and 


We thus have in the living being two distinct 
conditions of matter; the- one vitalized and essential to 
the life of the part, the other non-vitalized and sub- 
ordinate or accessory to the former. These, however, 
both depend for their continuance in existence on 
progression or constant motion of the fluids they 
contain ; otherwise stagnation in contact with the air 
leads to a change which develops one or more of 
the physical forces by the decomposition or decay it 

In addition to the continual passage of moisture 
through the substance of organic products in connection 
with the living organism, most of these bodies are 
perpetually undergoing a renovation or replacement by 
new, as the old portions are either taken up again or 
discarded from the system. Among the principal 
exceptions to the latter rule are the enamel and the 
dentine ; the former being never replaced, and the latter 
but partially so, and then only by an unorganized and 
almost structureless mass. 

Albumen, which enters largely into all organic forms, 
is composed of elements put together in such a manner 
as never has been effected by the hand of man. It is 
therefore termed "vital," and being a vital substance, 
the force which holds it together is designated the vital 
force. It has been supposed that this vital force, which 
has been instrumental in the production of all organic 
forms, is capable of migrating out of one form into 
another ; that vital force is given out in decaying wood, 
and becomes the life of the fungus which grows upon it. 
Professor Grove has shown us that all the physical 
forces " are correlative, or have a reciprocal depend- 
ence;" each one producing other forms, but "merging 
itself, as the force it produces becomes developed." 
Therefore in the decaying wood we have other forces, 
as heat, light, chemical affinity, &c, appeai-ing in lieu 


of it ; " it being an irresistible inference, that a force 
cannot originate otherwise than by generation from 
some antecedent force or forces ; " and heat and light, 
in combination with moisture, are known to be the 
most powerful abettors of life and growth. Organic 
matter exerts no influence upon other forms of growth, 
until the chemical force begins to set free the elements 
formerly held together by the vital force; and as all 
cryptogamic as well as other vegetation is known to 
arise from spores or seeds, and these spores containing 
within themselves the germ or condition of gTOwth, are 
teeming in every direction, wanting only the presence 
of moisture to start them into growth, together with a 
suitable nidus, which is here found in the decaying 
organic matter. The fact of seeds germinating in pure 
sand and water proves them not to be dependent on 
receiving vital force from other sources. Are we not, 
therefore, justified in regarding dentine as a vital body, 
but not possessed of vitality ? — as a substance composed 
of elements united by the force which is understood as 
the vital, but acquiring its physical condition of form and 
density through a physical force originating from the 
vitalization of the pulp and its vessels. 




The persevering' efforts that have been made to 
endeavour to interpret the formation of dentine by the 
cell-development theory, and the persisting in this course 
to the exclusion of seeking in other directions, has led to 
this being less understood than almost any other sub- 
stance to be found in the animal system. 

That cell-growth is concerned in the formation of the 
tooth is unquestionably true, but its action is limited to 
the production of the mould and its matrix or core, upon 
winch the dentine is deposited. The manner in which 
dentine commences and continues to form renders it 
necessary that some means should be provided by nature 
that the outer layer, which is the first to form, should be 
of the exact size and form of the future dentinal crown 
of the tooth. This is accomplished by the tooth papilla 
attaining, by cell-growth, a soft, pulpy mass of the 
dimensions required. But with the attainment of this, 
the vital part of the process to a certain extent termi- 
nates ; the vital force, no longer required for assimilating 
growth, merges into the electrical, and hence, by the 
action of a physical force, completes the transformation, 
or rather replacement, of the soft by its hard and stony 
successor. The pulp in its soft state is still covered with 
basement membrane and epithelium, but as the forma- 
tion of these substances is no longer required to be 
continued, the albuminous material which went to form 
them now begins to accumulate at the centres of 
ossification to form the basis of future dentine. 


Soon after this has commenced, it becomes tenanted 
by minute granular bodies, which, continuing to increase 
in size and quantity, ultimately assume the compact and 
dense form of a bony deposit. The granular bodies con- 
stituting the hardening element of bone, at one time 
were looked upon as " solidified cell-contents ; " but the 
true character of these formations has been fully demon- 
strated by Mr. George Rainey* as being nothing more 
than a peculiar form of crystallization of the salts of 
lime, due to the viscidity of the medium in which they 
are formed. 

These " artificial calculi," as they have been styled 
by their .discoverer, were obtained in great abundance 
from a viscid solution of gum acacia, but they were 
entirely isolated specimens in their most perfect form. 

By means of electricity the Author has succeeded not 
only in producing them in a very much shorter period of 
time, but also in obtaining a membranous matrix out 
of albumen, having within it ithese deposits in a definite 
layer, coalescing and aggregating together, and closely 
approaching the appearance presented at the edge of a 
natural bone in its early stage of formation. 

In electro-voltaic decalcification of bone, the salts of 
lime pass from the positive to the negative pair. 

Under the action of electricity, albumen is coagulated 
and rendered insoluble ;f but there is more than this, — 
it assumes a definite shape and structure, very much 
after the manner of iron filings between the two poles 
of a magnet. 

Around the negative pole is formed a cell-like sphere 
of highly transparent and glassy - looking substance 
(Fig. 16), while at the positive pole the mass collected is 
granular and somewhat opaque ; but intermediate, a wall 
of substance forms and spreads out right and left so as 

* "On the Mode of Formation," &c. G. Rainey, M.R.C.S. 
f Brande's " Manual of Chemistry." 



to separate the contents of the vessel into two distinct 


( V 7 Ui Me,'; <V ' I. 

Fig. 16. 


According to the law enunciated by Mr. Rainey, it was 
easy to foresee, that if viscidity were the true cause of 
the salts of lime taking the globular character instead of 
the usual form, by electro-decalcifying bone in a viscid 
solution, the salts of lime would be arrested in their pas- 
sage from one pole to the other, and take up their position 

within the coagulated albumen 
as a matrix. This they have 
been found to do, not in- 
discriminately, however, but 
aggregating together in a 
layer in the interior of the 
substance, forming the sep- 
tum or diaphragm c across 
the vessel between the two 
halves of its contents. 

Fig. 17 represents a ver- 
tical section in the line of 
the two poles, or at right 
angles to the diaphragm, 
showing also a free border 

Fig. 17. 

of unappropriated matrix on either side 



Fig. 18 is a square vessel, actual size, in which, the 
experiment was made. Fig. 19 is a vertical section of 
Fig. 18 from D to D. 

i ii 

Fig. 13. 

G, Fig. 19, is a piece of walrus ivory placed at the 
bottom of the vessel to furnish the lime transferred to 
the matrix c. 

z p 

Fig. 19. 

e is the negative wire and F the positive. The shaded 
portion of g shows the extent to which decalcification 
proceeded. Fig. 17 is a minute portion of c, in the 




<-o ' 


line dd. In mounting, it has been pressed out, so that the 
line of lime has become crushed down and spread out. 
Fig. 20 is a small portion further enlarged. The scale 
below each represents the hundredth of an inch ; Figs. 
17 and 20 having been traced with the camera. 

Fig. 20 is a more highly magnified portion of the edge 
of the lime, showing the 
globules coalescing into a 
more solid form. 

Fig. 7, Plate 2, shows a 
portion of the same, but with 
a piece of litmus test-paper 
applied to it while soft, show- 
ing the acid and alkaline con- 
dition of the opposite sides of 
the structure, with this com- 
plete similarity of proceeding- 
and corresponding nature of 
the results between the arti- 
ficial production of what may 
be termed bone-substance, 
and the natural process in the development of the 
tooth ; and as this occupies in nature the same rela- 
tive position in the peripheral battery of the system 
that it is found to do when produced artificially, there 
can be no hesitation in accepting them as being both 
produced by the same physical force. The peculiar 
structures which have hitherto caused so much perplexity 
as supposed " formative membranes," are here shown 
to consist of nothing more than a free and unconsolidated 
border of the membranous matrix. The cause of their 
separating readily as apparent membranes under the 
action of an acid or in suppuration, may be ascribed to 
a similar effect of the line of consolidated globules, as 
the fine of perforations produces in a sheet of postage 
stamps. There are various other minutiae traceable in 

D 2 

Fig. 20. 


the development of the natural organ, which may be 
equally illustrated by the same means ; but sufficient has 
been said to afford an ample demonstration of the fact, 
that the production of dentine is due to a physical 
force developed and fed by the vitality of the vessels in 
its pulp. What I have here sought to establish is, that 
certain i"tiix only of the living organism are endowed 
with " vitality/' or with that condition and arrangement 
of parts necessary to the accumulation and organism of 
organic material into organic forms ; and that as these 
organic bodies are then of themselves not required for, 
nor capable of organizing, other material, they are not 
endowed with vitality, but possess only plrysical proper- 
ties essential only for maintaining the persistence of the 
organic fabric. That these organic forms contain a force 
keeping them in combination, which we designate vital 
because it is not producible in any other way than as 
the result of life and growth ; and that as all the physical 
forces require some antecedent force, no force being able 
to originate itself, we have the vital force as the starting- 
point or great storehouse from which the physical forces 
emanate. And that as we have this vital force in the 
system correlated into motion in some cases, into heat and 
into chemical action in others, we have it also correlated 
as well into electricity, which has been shown to con- 
tribute certain definite characters and organic material 
corresponding in many points with natural products ; and 
hence it has been assumed with a very fair show of 
reason, that as the other physical forces are absolutely 
necessary to the 'production of animal forms, electricity 
should also be employed. 




The structure of the enamel has been described by all 
physiological writers as of a crystalline character, with 
the crystals prismatic and placed endwise to the pulp, 
and as being formed through the instrumentality of 
what has been termed " the enamel organ ; " but beyond 
this, no further advance appears to have been made in 
tracing out the laws of its formation. Now, it can be 
shown that the entire coating of enamel upon a human 
tooth is arranged as a portion of one 
of the globular crystals of lime, such 
as are formed in developing dentine. 

Fig. 21 is from one of the arti- 
ficial calculi given by Mr. Rainey 
at page 12, Fig. 4 a. 

Fig. 22 shows a circle filled up 
in the same manner with lines 
radiating from the centre to the circumference, 
corresponding in this respect with the Fig. 21. 
thin line drawn across will show an apparent section 
with the supposed enamel fibres, as seen in nature. If 
a pin be passed through the centre of the radiating 
lines, the tracing might be turned in any direction, 
while the radiating lines will retain their relative 
position, showing the centre of the enamel lines to fall 
somewhere near to the centre of the crown of the tooth. 
In a multicuspid tooth a very slight variation will be 
found in the action, being a tendency to produce several 
different centres, and give rise to a somewhat compound 
crystal, with as many short lines instead of a single 

Fig. 21. 





point for its centre. To obtain this coating of enamel is 
one of the main objects of the tooth papilla sinking 
down into the capsule within the jaw-bone. When the 

Fig. 22. 

dentinal papilla has grown to its full size, the capsule 
surrounding it forms a casing with the epithelium of 
the two surfaces in contact ; therefore the inside of the 
capsule must correspond in shape with the outside form 
of the papilla ; and hence, when the capsule is distended 
by the plastic mass of the forthcoming enamel, we have 
a mould which in some measure determines the shape 
and thickness of the future layer. 

The fluid or plasma of which the enamel is formed, 
"resembles in consistence the albumen of a common 
fowl's egg, and like it will run off an inclined surface. 
It has a sticky feel to the fingers, like a strong solution 
of gelatine."* We have thus the viscid medium required 

* Tomcs's Lectures. 


for giving rise to the globular form of the crystals, 
while the reason that one large crystal forms instead of 
a number of small ones, is evidently due to the attractive 
force of the one or more negative centres of the pulp 
overcoming the tendency of any weaker centres within 
the plastic mass itself; and being moulded to the interior 
of the capsule, is thus prevented assuming its own 
exterior globular shape, but is made to take that of its 



" The direction taken by the enamel fibre is, for the 
most part, vertical to the surface of the dentine upon 
which it rests ; those, therefore, which proceed from the 
fiat surface of the crown will rise vertically, while those 
from the lateral surface of the tooth will be horizontal. 
.... The ends of the enamel fibres are received into 
the shallow hexagonal depressions „ of the coronal surface 
of the dentine, from whence, in their course, they 
describe frequent curves." Such is the description 
given by Mr. Tomes in his Lectures, page 52 : of which 
the former portion relates to its normal state, while the 
latter refers to an abnormal condition produced by a 
disturbing cause during the period of its formation. 
The dentine, beginning to appear on the pulps, spreads 
over the surface of the latter, forming a thin shell down 
to the junction with the lower edge of the capsule. On 
its outer surface rests the basement membrane, upon 
which the enamel crystals are arranged. Fig. 9, 
Plate 1, has a portion of the transverse septum 
left attached, to show its positive or outer surface 
covered over with pit-like indentations, and this surface 
corresponds with the positive or outer surface of the 



Fig. 23. 

dentine. When this shell of dentine has formed upon 
the pulp, prior to any of the plastic mass of the enamel 
having become fully crystallized and adherent, the radial 

lines of the enamel will be 
straight, or normal, as in 
Fig. 23 ; but when the crys- 
tallization has commenced 
before the dentinal centres of 
ossification are complete, or 
the pulp fully matured, the 
cusps of dentine, as they 
become perfected, rise up 
into the semiplastic mass of 
crystallizing enamel and force 
or drag the adherent crystals 
with them in their upward course. This action will be 
clearly seen to have taken place, by the accompanying 

sketch, Fig. 24 ; the two 
cusps having produced their 
disturbing effect most upon 
the apex, but less and less 
downward towards the neck 
of the tooth. 

If on the completion of 
the dentinal crown and its 
commencing to rise by the 
growth of its fang, the whole 
of the enamel be sufficiently 
" set " to be elevated with it entire, the outer portion 
of the enamel attains a normal direction; otherwise a 
fresh set of curves will be produced on this part, rendering 
it also abnormal. 

It is but reasonable to conclude that any such inter- 
ference with the half- set crystallization must tend to 
weaken its attachment to the surface of the dentine, and 
render the enamel less homogeneous ; and not only is 

Fig. 24. 


there thus a tendency for the cohesion among its own 
particles to be lessened, but a curved line in the place of 
a straight one presents a physical defect, which, on the 
ordinary principles of mechanics, must offer a weaker 
resistance to outward pressure than the straight one ; 
and hence, this description of enamel will necessarily be 
weaker in resisting the effects of lateral pressure than 
the normal arrangement. The examination of a large 
number of teeth showing incipient decay, has led to the 
conclusion that the condition of the enamel in this 
respect materially influences the results of the crushing 
effects of lateral pressure, and that the more vitreous 
and dense, that is, the more perfect and normal, the 
crystallization of the enamel, the less does it appear to 
be the subject of injury. 



1. That dentine can have no claim to be considered 
as possessing " vitality," but that it is simply a vital 
product in an organic form. 

2. That the vessels of the pulp — namely, the nerve, 
artery, veins and their capillaries, together with the 
vessels from the periosteum, are the only parts of the 
tooth endowed with " vitality." 

3. That the pulp-vessels, together with the dentine 
and its enamel, in conjunction with the albuminous fluid 
with which they are moistened, form an electro-voltaic 
series, and are a portion of the peripheral battery of this 

4. That the result of such an electro-voltaic arrange- 
ment is to withdraw albuminous material from the blood 
circulating in the vessels of the pulp, and to effect its 
consolidation according to certain fixed laws. 

5. That the formation of dentine is due to this electro- 
voltaic action. The growth of the dental papilla to the 
size and form of the future tooth being purely an act of 
vitality, the subsequent deposit of membranous matrix ; 
together with its becoming filled up with the salts of 
lime, are clearly demonstrated, by the artificial production 
of bone-substance, to be due to a physical or electro-voltaic 

6. That any seemingness of vitality in the dentine 
may be ascribed to its being imbued with albuminous 
fluid, and constituting the positive elements of a galvanic 
series, of which the negative is supplied by the negative 
vessels of the vital pulp. 

7. That local action in an electro-positive element 


constitutes the decalcifying and acidifying process in 

8. That as some forms of carbon are among the most 
powerful electro-negative bodies in nature, this local 
action is first started by an electro-negative point of 
carbon, or by some want of homogeneity in the enamel 
or dentine. 

9. That it occurs in pits, fissures or porous parts of 
the enamel through a deposit of carbon, or by erema- 
causis of the membranous matrix, the organic portion 
of the enamel and dentine. 

10. That a minute portion of carbon forms an electro- 
negative centre, has been shown by the carbon placed in 
the notch of specimen No. '5, Plate 1, having protected 
that side of the tooth from electro-positive action. 

11. That the supposed death of the dentine is simply a 
well-khown description of decomposition, common to all 
organic matter, and known as eremacausis, or slow 

12. That the carbonaceous substance resulting from 
dry decay is at first alkaline or neutral. 

13. That it is only when it has become saturated with 
stagnant moisture that electrolytic action commences and 
acid is formed. 

14. That plain water is capable of producing an 
electrolytic decomposition of the dentine, and leaving 
acidity in the decalcified tissue, but that fluids containing 
inorganic salts produce more extensive action. 

15. That sugar and water produce a more decided 
effect than plain water, but that saliva is by far the 
most effective agent. 

16. That the various acids to be found in the mouth 
are derived from the separation of acids from their bases, 
together with the oxygen, obtained from decomposition 
of the water forming the electrolyte, combining with 
different organic bodies, or their elements, contained in 
the saliva as it comes from the ducts. 


1 7. That substances taken internally are to be traced 
in the saliva, is shown by the voltaic detection of iodine 
after taking small doses of iodide of potassium. 

18. That in respect to the progressive decomposition 
of decay, the enamel is sometimes found corroded in 
holes before any signs of decay have become apparent 
in the dentine (a, Fig. 2, Plate 1), showing the organic 
matter mixed up with the enamel to be affected similarly 
with the matrix of the dentine. 

19. That the transparent zones of Tomes, or con- 
solidation of the dentinal fibrils, is frequently the first 
change that takes -place in the dentine. (Fig. 4, and a 
and b, Fig. 2, Plate 1.) 

20. That when albuminous fluids are acted upon 
electro-voltaically, the albumen becomes consolidated in 
a definite form — granular and somewhat fibrous at the 
positive pole, highly transparent and jelly-like at the 
negative, and with a densely -formed wall of substance 
transversely between them. 

21. That when dentine is electro-voltaically decalcified 
in albumen, the consolidated portion between the two 
poles receives a deposit of globular concretions of lime, 
almost identical in appearance with similar concretions 
seen in the edge of newly-formed dentine. 

22. That in all deposits formed in albuminous matter 
by electricity, a free border of transparent matrix remains 
unappropriated, which corresponds with the transparent 
rings and periosteal layer of bones and the so-called 
formative membranes in the teeth. 

23. That the zones of secondary dentine, as also the 
portions of granular concretions, adherent to the cavity 
or scattered in masses within the substance of the pulp, 
are due to the electro-voltaic deposit induced by local 
electro-voltaic action, and that consequently calcification 
of the pulp is to be induced by the same means. 

2 1. That in the consolidation of albumen electro- 


voltaically, the negative side is always alkaline, wliilc 
that formed at the positive side is invariably acid. 

25. That in this respect it corresponds with the layers 
of the skin, where the blood-vessels, in health, are 
alkaline, while the epidermis and epithelium are acid. 

26. That it is this condition which produces the acidity 
in the mucous surface of the gums. 

27. That in every instance in which acidity can be 
traced in decaying dentine, the vessels of the pulp will 
invariably be found to be alkaline or neutral ; thus indi- 
cating then* different electro-voltaic condition. 

28. That the lateral spreading of a carious cavity, and 
its not more extensively opening out the pulp-cavity, is 
due to the electro-negative or opposite condition of the 
pulp serving as a barrier for its protection. 

29. That the dentinal fibrils exert the same negative 
tendency in protecting the walls of the dentinal tubes, 
causing " the intertubular substance to be first, and the 
walls of the tubes the last, to disappear ; " and hence the 
improbability of effecting the same condition artificially. 

30. That the decalcified surface of a carious cavity 
continues in a negative state as the decay proceeds, and 
thus keeps up the local action as it extends its area. 
(Fig. 10, Plate 1.) 

31. That it is only after having lost the protecting 
influence of the healthy pulp that the cavity has its nega- 
tive condition overcome by the positive and merges into 
the decaying surface. 

32. That decay may be produced and carried on arti- 
ficially by electricity, although the decalcified tissue 
requires the effect of time to accomplish its discolo- 

33. That the notches at the necks of the anterior 
teeth greatly resemble the effect of local electro-voltaic 
decalcification of healthy dentine, as produced by these 
means in Figs. 13 and 14, Plate 1. 


34. That as too viscid a state of the albumen used in 
the electro-voltaic experiments was found materially to 
prejudice the condition of the deposit of lime, so the 
state of the albuminous fluid of the system going to 
form the dentine may be supposed to exert a similar 
influence on the texture and hardness of the tooth as 
well as on its predisposition to decay, and thus account 
for the difference in this respect occurring in different 

35. That as the structure of the enamel shows it to be 
a portion of one of the globular crystals of lime formed 
in a viscid material, the so-called enamel fibres are but 
the characteristic features of the radiating form of its 
aggregated atoms. 

36. That as the radiating fines in the enamel in their 
normal form are straight, the curves formed at the cusps 
are abnormal and due to a disturbing cause during the 
growth of the tooth, which, by disarranging the accu- 
mulating crystals of enamel before attaining their full 
consistence, may lessen then' cohesion and thus predispose 
the parts to decay. 

37. That the dentine forming the crown of the tooth 
being produced in lieu of, and occupying the place of, 
the cuticular layer of the skin, is consequently in a corre- 
sponding electro-positive state ; but that the fang being 
encased among the negative vessels of the cutis is 
normally electro-negative, and hence, like the surface of 
the cavity in b, Fig. 10, Plate 1, its negative condition 
induces the formation of tartar, which settles upon it ; and 
also in decay prevents the cavity spreading down 
between the pulp and the periosteum much below the 
attachment of the latter ; but when denuded of its 
covering, and its connection cut off from the vessels, the 
exposed portion merges into the electro-positive condition 
of the crown, and thus becomes the victim of decay. 

38. The influence of electricity is so palpably mani- 


fested in the generation of the tooth-coverings — sub- 
stances which are not liable to the same changes of 
absorption and reproduction as occur in the vital parts, 
and as the effect of every voltaic series is not that of 
combination alone, but includes decomposing powers as a 
part of its constitution, we can scarcely refuse to accept 
the decomposition of the tooth-substance as arising from 
one or more contingent circumstances connected with 
the same arrangement which has constituted the com- 
bining force in its production ; and more especially as 
the effects arising in the mouth correspond so closely 
with the results obtained artificially by the same means.